Transmission



Aug. 20, 1963 Filed may 27, 1957 l H. w. cHRlsTENsoN ETAL,

TRANSMISSION 3 Sheets-Sheet 1 |||||||I| Illlllm umm@ /A/VE/VTORS Aug-20, 1963 H. w. cHRlsTENsoN ETAL 3,101,012

TRANSMISSION Filed May 27, 1957 3 Sheets-Sheet 2 U Arron/Mfr Aug- 20,1963 H. w. cHRlsTENsoN ETL, 3,101,012

TRANSMISSION Filed May 2'?, 1957 determined value.

United States Patent O rllhis invention relates to a transmission andahydiaulic control system.

The transmission is particularly adapted for use with turbine drives andprovides six forward speeds and two reverse ratios. -r[he planetarygearing consists of a ront un-it providing two speeds and a rear unitproviding three speeds and reverse which are combined to provide for sixforward ratios and two reverse ratios. The control system employs amanual selector valve which will supply uid to a ratio device such as aclutch or brake in each unit to provide these ratios. VHowever, duetothe heavy inertia torques that yare encountered in gas turbine enginesdue to the high rotational inertia of turbines it was `found necessaryto limit the loads on the tnansmission and drive gearing to avertfailures. rIn the present transmission arrangement it was foundnecessary to limit stresses or loads on the rear gear .uni-tparticularly during shifts `from one range to another since .the changein momentum involved in speeding `up or slowing down the gas turbinetends to cause high peak torques when the change `in momentum occurs toorapidly. The control system `is arranged to disengage the ratio devicesof the front unit during each shift interval, to re-engage the ratio`device of the front unit after 'the ratio idevice `of the rear unit isfully engage-d, and to limit the rate of engagement of the ratio deviceof the front unit so that :the torque transmitted through thetransmission is limited to a pre- The front unit ratio devices aredisconnected during each rear unit ratio change by a cut-oil valve inthe line supplying tluid to the front unit ratio devices which isactuated by iiow through the ratio supply line to the rea-r unit ratiodevices which disconnects the frontunit supply whenever a rear unitratio device is being supplied with fluid. In addition the pressuresupply to the front unit ratio devices is controlled in proportion tothe torque being transmitted through the transmission to limit themaximum torque transmitted to a predetermined value. When the outputoverruns the input, i.e., during down-hill coasting, it is desirable tolimit the maximum speed of the turbine. This is done by disconnectingthe front unit ratio `'devices by an overspeed cut-oil valve which`disconnects the supply to lall the'front unit clutches in response toengine overspeed indicated by the transmission governor. Y

An object of the invention is to provide in a multnatio transmissionhaving two gear units connected in series, an automatic control systemin which the ratio change devices `of one unit are disengaged `duringthe ratio change mission having a front gear unit and a rear gear unit tconnected in series to provide a plurality of ratios, a `contnol systemin which one unit is disengaged whenever a ratio change occurs in theother unit and torque respon- 3=,ll,ill2 Patented Aug. 20, 1963 ice iUREl showing the pitot governor.

p FIGURES 3 and 4, Iwhen arranged in accordance with the diagram inFIGURE 2, schematically show the hy- -draulic control system.

VThis transmission, particularly designed for use with high-speedengines such as gas turbine engines, has a two speed front unit and athree speed :and reverse rear unit providing six forward drive ratiosand two reverse drive ratios. The control system for the ratiochangegearing will cause a front unit ratio clutch to slip or disengageto provide smooth shifts, to limit the torque to protect thetransmission and the drive train against overloads and to limit thespeed to prevent excessive engine speeds on output overrun, ie., forvehicle xtransmissions under downhill overrun conditions.

The transmission assembly has serially connected a reduction gear uni-tlll, a front unit L11 providing two ratios, and a rear unit 12 providingthreerforw-ard natios and reverse. As will be explained in detail belowthe front gear unit and the `rear are combined to provide six forwardratios and two reverse ratios. The `output shaft from a gas turbine orother suitable high-speed engine is connected to the transmission inputshaft 16 which drives the sun gear `17 of the planetary reduction unit1li. The sun gear meshes with planetary pinions 18 which are mounted ona carrier '19' or transmission input member. The input member @19 isdriven at a slow speed since the ring gear -21 is substantiallystationary.` The torque meter device 22 holds the ring gear stationaryand. provides a pressure proportional to the torque being transmittedthrough the reduction gearing 10 and the transmission. The input member19 has a power take-olir gear 23 mounted thereon which drives suitablespur gear 24 which may provide the `drive for various accessories suchas the input driven pump and the input drive pitot governor.

The pitot governor can 26* may also be mounted directly on the inputmember y19.. The can 2li has a generally `annu-lar shape and acylindrical internal portion which press -lits over the outercylindrical surface of the input member 19 asshown in FIGURE l and has aflange ZSsnapped or bent into the groove in member 19.

.The other pontionyof the can 20 extends substantially radially out fromthe input member and is reversely bent to provide an annular chamberIopened at the inside for the uid 'which is retained in the chamber bycentrifugal force.

AIn the `front planetary gear Aunit 11 the input member 19 drives thering gear 26 which meshes with the planetary pinions 27 mounted on theoutput carrier 28 fixed to the output shaft 29. p The sun gear of theiront unit 11 is iixed to a control hub 32 which may be stopped toprovide nnderdrive by a brake or ratio device 34 which includes a fluidmotor 36 lor which may be connected to the input member 19 to provide aldirect drive when the clutch or ratio device 38 which includes fluidmotor 39 is engaged. Thus the input member 19 will be connected to drivethe intermediate Youtput shaft 29 in [direct drive when the clutch 38 isengaged and in underdrive when brake 34 is engaged.

' to the output shaft 46. The pinions 43 also mesh with therinlgrgear`47 which may be stopped to provide first or low ratio by engaging thebrake 48 which includes a iuid motor 49'. .The second sun .gear 42meshes with planetary pinions 51 which are mounted on Va carrier 52which is connected by the hub 53a to the ring gear 47. Pinions 51 alsomesh withering gear 54 which may be stopped by the brake Siwhiohincludes the fluid motor 5710 provide` intermediateratio. l The VVringgearr54 is also connected by a clutch V61 which includes Vthe duid motor62 rfor actuating the clutch to connect the ring gear 54 through the hub63 to the intermediate shaft 29 to'provide ldirect'qdrive or high inrear unit 12. YThe reverse-gear set has a plurality of planetary pinions66 mounted on a carrier 67 connected to the :output gear 68 and shaft46. The planetary pinions 66 mesh with `a sun gear 71 which is connectedby .hub 72 to ring gear 47 and with a ring gear 73 Which'may be stoppedto provide reverse byfengaging brake 74 which includes Va uid motor 76.V VThe above brakes 48, S6 and 74 'and clutch 61 areratio devices.

` The output shaft 46 and gear 68 provide kthe final drive of thistransmission. Where the transmission is usedfor an industrial drive lorin a vehicle drive requiring a single input such as a conventionaldifferential vehicle drive' the drive @gear 63 is the output member'.Where it is desired to Iuse* "this transmission in connection with apower steer crossdrive unit of the type shown in the applicantsco-pending application S.N. 484,122, tiled January 26, 1955, ,no-WPatent No. 2,930,257, entitled, Transmission, the intermediate outputshaft 29 may be extended through the shaft 46 and connected by gears 78and 79 to the auxiliary power shaft 81 which is employedY to provide apower -for steeringthe onossdrive transmission.

Hydraulic Control System The'hydrauiic control system supplied withiluid from the transmissionA sump by line 91 which supplies iuid` f to alirst input idriven pump 92 and second inputdriven pump 93 and outputdriven pump 94. The first input pump Iwhich may be driven by theaccessory gear 23 supplies duid under pressure through line 96 Itosupply Y the torque meter 22 with uid under pressure While the secondinput driven pump which may valso be `driven by gear 23 supplies duidunder `pressure to main line 97. 'Ihe output driven pump which may bedriven Vby the output shaft 46 tor drive gear 68, supplies the mainline-97 when the transmission is operating in a forward ratio.

nection,` to the central portion 1116 of the double ended `'piston 107to axially move the piston in the cylinder when- '.ever the rin-gfgear21 moves. rThe cylinder 101 has an annuels `to cylinder end 117 and 119respectively and exhaust 121 at the center of bore 1119. With the piston1117 in the central position, the port 112 is connected to a pas- Sage116 communicating with one end 117 of the cylinder while the port 114 isconnected by a passage 118 with the other end 119 of the cylinder 191and these passages 116 and 118 :are y.also connected by the groove 111to exhaust 121 and slot 1113 through which iluid is returnedto thetransimission sump.

When the for-ward torque reaction force :on the gear' 21V moves vthe arm1112, ttor example, to the right as shown in FIGUREv 3, the piston 1117isv moved to the right closing port 112 and the connection between thepassage 118 and groove 111 to exhaust 121 so thatl supply line 96 isconnected through the tube 1138, port 114,V and passage 118 to' the end119 of thelcylinder v101. This pressure will be proportionate to thetorque reaction on the gear 21 since anV excess pressure in the cylinderend 119 will move the piston back to :open exhaust 121. Thus la pressureproportionate to the torque reaction gear 21 is supplied to line 123.71Theaother cylinder lend 117 is Vsimulftaneously connected by passage116and groove 111 to exhaust `121 so no pressure is supplied to line '124.Movement of the `arm 1612 in the opposite rdirection by reversetorquereaction on gear 21 similarly provides.

` pressure in cylinder end 117 proportionate to the torque reactionwhich is connected by line 124. Lines 123 and 1241 a-re connectedthrough. a dou-bie acting check valve 126 to the torque signal line 127which supplies pressure proportional to the torque transmitted throughthe,

transmission during bothtforward and reverse drive.

Supply line 97 is connected'throfugh a rilter 131 or,

when there is an excessive pressure ldropinthe iilten through the lterby-pass valve 132 to the main line 135l whichV supplies the rear 'unitclutches., `rlhe pressure in the main line 133 is controlledby a primaryregulatorV valve 136 having a piston 137 Iwith a small landga and aVlarge land b located in a small bore 138 and a lange bore 41359respectively. The valve element 137 has a port 141 in land a connectedby passage 142 extending axially through the valve tothe end face of theland b. rIlhe end or thegsmall bore'pontion 138 1 is connected to theratio signal line 144 which provides a pressure in neutral, and third tosixth ratios acting `on the end ofthe land a to decreasethe pressurefrom the normal high pressure, i.e., 225 p.s.i. to a lower value, i.e.,110 p.s.i. The main iine 133 is connected to a port l146 between thesmall bore 138 and large bore 139 so y that the iiuid pressure acts uponthe unbalanced area be- V manner lnot shown, for example, by a pin andslot con- Y axialtube 108 ixe'd and sealed to the cylinder. The tube Yis connected to the torque meter supply line 96 and closed at theopposite end [of tube 1118 and ts within an tween lands aV andfb to movethe valve toward the exhaust position.

pressure. When the pressure in main line 133 reaches the regulated valueand acts upon the unbalanced area the valve element `137 moves againstspring 147 toexhaust the excess fluid, first by opening port 148connected to the secondary;l main line 149, andy 'second by connectingport-146 through port 141, passage 142, `and the spring chamberportionof bore'139 to exhaust 151.

The pressure lin the secondary main line 149' supplies the front unitclutches and is regulated by the secondary regulating valve 154 at -apressure (i.c., 100 p.s.i.) less than thelower value, pressure regulatedlby the primary regulator valve 136. The valve 154.1r has a valveelement 156 located inthe bore 157. The secondary line 149 is connectedto' one end of the bore 157'and acts on the end of the valve element 156to urge the valve to the other end ofthe bore 157 against the spring1611 which is located 156 to open port 15S to the cooler line 159. lfport 158 does not provide suilcient capacity to reduce the pressure `inline 159 to the regulated value the line L49 will also be connected at'port 161 through port 1152 in valve ele- A spring 147 engages the endof theV pbore 139, and the vvalvev element 137 to bias the valve towardthe closed position toregul-ate the normal high ment 156 and bore 157 toport 162 which is also connected to the cooler line 159.

Cooler line 159 is connected through the cooler 166 or through thecooler by-pass valve 167 in the event the pressure differential acrossthe cooler is excessive, to the low-pressure supply line 168 which isemployed to `sup-` ply fluid at a low pressure, i.e., 30 p.s.i., to thetransmission lubricating system 169 and the pitot governor feed`connected to the main line 133 through a one-way checkA valve 183 bypassing orifice 181. p

The torque limiting valve 186 has a valve element V187 having lands aand b `of equal diameter located in a large diameter portion 188 of bore189 and a small diameter land c located in a small diameter bore portion191. The valve element 187 has a stem i192 extending from land a whichlimits the movement of lthe valve and provides a guide for the spring193 located in the spring chamber portion 194 of bore 189. The springchamber is provided with an exhaust 196 to avent uzid being trapped andinterfering. wvith the operation of the valve. The torque signal line127 is connected in all tof ratios to the bore between large and smallportions to act on the unbalanced lands b and c to move the valveagainst the spring. The ratio controlled torque signal line Y197 isconnected by manual valve 256 to supply fluid from the torque signalline 127 whenever the front unit is inlow and thus the transmission isin either rst, third, or iifth forward ratios or the iirst reverseratio. 'Ihis ratio control torque signal line `197 is connected to theend of the small bore 191 and acts on the landc together with torquesignal pressure line 127 acting on the unbalanced area between the landsb and c to oppose spring 193 to further reduce the pressure. TheYsecondary main line 149 is normally connected between the lands a and bof the valve element 187 to the torque controlled main line 198.

When the torque exceeds a predetermined value, i.e., 4000 foot pounds inintermediate shaft 29, the torque signal pressure will close the valveand land b will close the port of the main line 149 and open line *198toexhaust 199.' If the clutch motors are filled the cut-oli will beabrupt. Howevenif they yare being iilled, due to theflow to the motorsand the bevel on lands a and b, the flow and pressure will be graduallyreduced to slip or disconnecta front unit clutch to limit the torquetransmitted.`

When the torque is reduced the torque signal pressure is Areduced andland a will close the exhaust 199 and recon? nect main line 149 betweenthe lands a and b to line 198 to supply thefront unit clutches. Thetorque meter 22 provides a signal pressure proportional to input shat 16torque. Since the intermediate shaft 29 torque varies with respect tothe input torque in accordance with the front unit gear ratio, thetorque signal pressure acts on the unbalanced area of land b when thefront unit 11 is in high ratio and on this area and the area of land cwhen the front unit is in low ratio to close valve 186 at a lower torquesignal pressure since the torque in the intermediate shaft is greaterthan the measured input torque due to the gear ratio. Thus the torqueinthe intermediate shaft is lirni-ted to the same value in both frontunit ratios.

The torque limiting valve 186 may be provided with hysteresis by aslight decrease in the size of land a of valve element 187 and theportion of the bore in which it operates. Then the line pressure betweenthe lands a and b would provide a force-resisting movement of the valve187 to the closed position. Since this force would The cut-oft` valve206 has a valve element 209 having a t not be present to move the valvefrom the closed to the `the front unit clutches whenever the uid issupplied from the primary main line 133 to the rear unit supply line208.

small land a located ina small bore portion 211 located at the upper end`of the bore 212 and lands b and c'and d of larger diameter locatedinlarge bore portion 214. The ratio signal line144 supplies pressure whenthe transmission isin the third, fourth, lifth, or sixth ratios or Whenthe intermediate clutch 56 or the high clutch 61 of the rear unit isengaged to the closed end of the small bore por-tion 211 to act on thelend land a. When th-e transmission is operating in a ratio fluid issupplied from the main line 133 through the oriiice 216 between thelands a and b` to the rear unit supply line 208. The flow through theoritice will be sutlicient to supply fluid to make up for any leakagewithout creating a pressure differential suilicient to actuate thevalve. However, when a shift is made by moving the manual valve 256,requiring a change of ratio in the rear unit, flow from line 133A toline 208' across the oriiice 216 reduces the pressure between the landsa and bfpermitting the spring 217, located at the other end of thevalve, to raise the valve to the shift position. The valve 206 willupshift and downshift at points on the clutch pressure rise curve having`the same proportion to the maximum pressure in line 133, since when themaximum pressure in line `133 is lowered by the action of ratio signalpressure in line 144 on regulator valve 136 the ratio signal pressurealso acts on land a of Valve element 209 to modify the action of thevalve element.

In the closed position land a open-s the unrestricted lbranch 218 ofline 133 between the lands a and b to line 208 to provide anunrestricted supply of iiuid 'to the ratio clutch being engaged. Val-ve206 normally connects the throttle cut-off line 221 between the lands band c to exhaust 222 but when ya shift occurs in the rear unit and whichis normallyconnected between the lands c `and d' Vto a cutol main line42017, is blocked, when valve 206 is in the shift position, =by land d.and line 207 .is connected lb-etween the lands c and d to the exhaust222 to disconnect splitter ratio devices 34 and 38 during each rear unitshift. The stem 226 which may lne secured to the valve element 209 or tothe end of the bore 212 provides a guide tor spring l217 and limitsthemovement of the valve 209. The enlarged end portion of bore 212 in whichthe spring 217 is loc-ated has an exhaust 227 to prevent interferencewith theoperation of the valve. l Ward movement of the valve.

The eut-ott main line 207 is connected to the overspeed Ivalve 231 whichdisconnects the supply of iiuid to the tron-t unit supply line 232 tocu-t off the supply of fluid to the |front unit clutches and disengagethe transmission `drive to limit transmission speed to protect thetransmission against excessive and dangerous speeds. The valve 231 'hasa valve element 233 having a small land a in the small portion 234 lofbore 236 and large lands b and c located in the large diameter lboreportion 237. A pitot governor 241 having a cam 242 which may he as shownin FIGURE la or rotated by the power take-oit gear 24 The shoulder 228limits upl unit supply line 2%.

clutch line 262' to'engage the fhigh clutch 6i.

and supplied wit-h `iiuid by the pitot `feed line 171; has a lpitot tube2t?)V -whiohsupplies fluid at a pressure proportional to transmissioninput speed to the `governor line 244-.

The governor line y244i is connected to the end of small bore portion23d so that the governor pressure acts onV the end of land a ofvalveeelement 233 to urge the valve an exhaust 247. When thetransmission speed is below a predetermined value, considered safe,thevalve 233 will Ibc inthe posi-tion shown connecting cut-cti line 267`be- Y tween'th'el-ands b and c to theiront unitsupply line 232. Whenthe speed of the transmission is vabove 4the pre-d determined spered,governor pressure on vland ci will move the valve'ZSSiagains-t thespringzie closing exhaust' 252 lconnecting the Iline 2d? to the' axial,groove 2419 and the space between'the lands a 'and b where thefluidwill act on the `unbalanced area of land a to provide hysteresis.

` `against spring 246 located in the opposite end of the large y boreportion 237. lThe spring portion of bore 237 .hasV

rfthe-front unit supply linc232 will then be connectedl between landsbaud c to exhaust 251i to `disengage -t-he :front unit ratio clutchesThe hysteresis action of the valve pre- The manual lcontrol valve 256constructed in `accord- 'ance with theteachin-g of FIGUR-ES 7 and 8 ofVPatent 3,016,769 Christenson et al., filed May 18,1955, is a rotaryvalve having nine .positions providing six forward ratios, neutral andtwo reverse ratios. The valve 255V has ya fixed plate shown .and arotatable plate .madeV as taught in Patent 3,016,769 to provide theyfollowing connections. The Vmanual valve 256 in .the neutral positioncuts oit both the `front unit supply line 232 and the rear i In firstratio 'the rear unit supply 26S is Vconnected .to the low clutch line257 to supply the low clutch 4S and the iront unit supply line 232 .isconneotcd to the front unit low clutch line 258 .the clutch 34. In thesecond the rearunit supply line 203 remains Y connected to the lowclutch line 257 and the front unit supply line 232 is connected to`front unit high clutch line 259 and the olutch. VIn third ratio therear unit supply line V2% is connected `to the intermediate clutch line261 `and clutch 56 -and the front unit supply `line 232 is lconnected tothe iront unit lowV line 25,8. For .fourth ratio the intermediate clutchclutch' 56remiains engaged and` the front Vunit-supply line 232 isconnected to the,v frontY unit high clutch 38 by line 259. In tif-th and-sixth ratio the rearunit supply line 263 is connected to the high Thelfront unitsupply line l23:2 is in iiith ratio connection to the lowclutch line S and in sixth to the high clutch Aline 259. In reverse therear unit supply line 2981's convents reengagement of the front unitclutches .until the i speed drops Va predetermined value.

regulator valves during the initial period of clutch ap. plicationregulate the pressure at a low value and then gradually increase thepressure to main line .pres-sure. When the clutch pressure rises above`the initial low regulated value, this pressure being-connected to bore271 Vmoves valve element v272 against the spring 273 perrnittingtheexcess liuid to the exhaust through exhausts 274 and 27S to `maintainthe pressure at a lowvalue controlled by the spring in` the positionshown. At the Y same time the fluid passes throughvthe lay-pass pass-age276 which at this time is yblocleed fbytheone-way check 'valve'.i'P7 sothat .liuid'iiows through the orifice by-'pass passage 278 to the otherend of thevalve'bore 271 `where the iiuid acts on the-piston abutment.279 for use .spring 273 andY moves the .abutment toward thevalve"element 272. This increases thelspringfforce acting'cnlthevalvef .andthus Vthe regulated pressure in clutch line i259 tornai-n 4 linepressure. The otherregulator valves .267- -26i iunc ltion and operatewith the sam-e manner to regulate they pressure `front low clutch line258 andthe rear high clutch line 262 respectively.

l i Operation y Transmission is operated to engage a selected ratio by`the manual valve 256. As pointed 'above this valve in vthe iirstthirdVand iifth ratios suppliesiiuid to the front unit low clutch line 258 andrespectively to the low, intermediate .and high clutches of the rearunit. In second, fourth and s'urth ratios the front high clutch 38 issupplied and the same l'oW, intermediate and high clutches of the rearunit are supplied respectively. Whenever a shiitv is made requiring oneof the rear unit clutches to' he filled,

such as a -second to third ratio change, a ow of fluid to theintermediate clutch through the rear unit supply line 208 actuates thecut-oil valve 2426y tocut oif the supply of v Viiuid to the front u nitsupply line 232.- 'Ihus any clutch in the front unit whichl is engaged,in this example the front high clutch, will be disengaged and then4reengaged when the rear unit clutch being filled is Vsubstantiallyengaged.

Then'pressure on both sides of the orice 216 equalizes permitting thecut-olf valve 206 returnto the normalposition and reconnect the. line109 to supply line 207 Vand the front unit supply line 2,32 to engagethe front unit clutch.V This arrangement makes it possible to provideminimum capacity rear unit clutohesand to accommodate all the slip inthe front unit clutches which have a larger Y heat capacity' -an'd aresufficiently cooled to take this nected to the reverse clutch line 263-tol provide in a R1 posi-tion' .a low reverse ydrive when the' frontunit supply line 232 is `connected to the low line 2S?, and'in the R2position the high vratio reverse drive by connecting this line to clutchline 259, The manual valve 256 also con- Y nects in iirst,wthird `andrifth forward ratios and the first reverse ratio the torque lsignal line127 to :the ratio torque Y .signal line 197 to supply additional fluidto the torque limiting valve 186 whenever the Iiront unit low clutch isengaged, since :duet-o the nature of .the gearing less pressure isrequired on the low clutch to transmit 400i()l `foot 'pounds of torquethrough the transmission than on the high clutch.` This arrangementmodies Ifront unit clutch y extra load upon each shift. Also the frontuni-t clutches fare both controlled to provide smooth engagement by theregulator valves266 `and 267.

' Whenever the torque being transmitted by 'the Vtr'ansi 'i missionexceeds a safe value, ie., 40005 foot pounds, the

pressure supplied by the torque meter movesthe valve f against a spring193i iand gradually restricts or reduces Ythe pressure of the fluidsupply from main line 149 tothe .Cut-off line 193` and frontunitsupply'line '232 to cause thefront unit clutches 34 or 4S to slipcrabeY disconnected to limit thetorque being transmitted. f Since theiront |low clutch 34 requires less packing pressure to transvmit 40G()foot pounds of torque, whenever the low clutch is engaged, torque signalline 127 is connected by the manual valve to the ratio torque line 19710act on an additional area of the torque limiter valveto restrict thepressure supplied lto the iront unit supply line 232 `to the front unitclutches at a lower value or torque signal pressure.

To protect the transmission against overspeed, the governor 241 suppliesthe uid via the lgovernor line 244 to the overspeed cut-oli valve 231and moves this valve to disconnect the supply `line 207 from line 232which supplies the fron-t unit clutches 34 vand 38V to disengage theseclutches. As this valve 231 moves tothe cut-cti position land land acloses exhaust 252 and passageV 249 connects the supply to theunbalanced area between the lands a a-nd b to provide an `additionalforce to hold the 9 valve in the cut-off position. 'I'hus the valve willnot move -to the open position until the engine speed is reduced bypredetermined value below the maximum allowable. This arrangementprevents, during down-hill coasting or other input overspeed conditions,the load driving the engine at excessive or dangerous speeds.

The above described embodiment is illustrative of the invention 'and itwill be Vappreciated by those skilled in the artthat variousmoditications may be made within the terms of the appended claims.

We claim: e e l. In a transmission assembly, a first gear unit providinga plurality of ratio drives, Ia second gear unit vproviding a pluralityof ratio drives, connected in series with said first unit, control meansto selectively engagea ratio Adrive in said iirst unit and 1a ratiodrive in said second unit to provide a plurality of combination ratiodrives normally transmitting the full power applied to said lirst unit,means responsive to a predetermined value of torque being transmitted bysaid units operatively connected to said control means to partiallydisengage the drive ratio engaged in said first unit to continue `totransmit torque `means to control the pressure of 'die liluid from saidsource to provide a low and a high iiuid pressure, valve means tocontrol the supply of fluid from said source in each ratio position toengage two of said fluid actuated ratio engaging devices to provide eachdrive ratio, control means eifective only `during the engaging Vmovementof one of said ratio engaging devices to insure disengagement of anotherof t said ratio engaging devices operative in each drive train ratio',`said `control means being effective when said one ratio engaging deviceis` engaged to engagesaid other ratio engaging device, and means tomodify the action of said l0 in each ratio by said front unit to saidintermediate shaft to the same torque value, governor means to supply apressure proportionate to the speed of said input member, and meansresponsive to said governor pressure to cut ot the supply of lluid tosaid fron-t unit supply line to disengage said front unit. v

4. In a transmission, an input member, an intermediate member, an outputmember, a front unit providing a plurality of ratios and having iluidoperated means to engage each ratio connecting said input andintermediate members, a rear unit providing a plurality of forwardratios and having uid operated means to engage each saidrear unit supplyline to one of said liuid operated t ratio connecting said vintermediateand output members,

a source of `fluid under pressure including a front unit supply lineandu a rear unit supply line, selector valve 'means to selectivelyconnect said front unit supply line to one of vsaid fluid operatedmeansof said lfront unit and means of saidrear unit in various combinationstoprovide a plurality of drive ratios for said transmission assembly,valve means responsive to the flow of liuid. through one t of saidsupply lines to cut off the flow of iiuid through the and to limit thetorque transmitted to a predetermined other of said supply lines,`torquesensing means connected to said input 'member toprovide a signalpressure proportionate to the torque being transmitted by said inputmember, and torque limiting valve means responsive to said torque signalpressure to limit the pressure supplied to one of said supply lines tolimit the pressure to said tluid operated means to limit the torquetransmitted by the transmission. t

5. Ina transmission, an input member, an intenmediate member, an outputmember, a front unit providinga plurality of ratios `and havingfluidoperated means. to engage each ratio connecting said inputandintermediate members, a rear unit providing a plurality of forwardratiosand having fluid operated means to engage each ratio connecting saidintermediate` and output members, a source control means to effectdisengagement and engagement of said other r-atio engaging device whentheengaging pressure at said one ratio engaging device is changedbetween said lou.r pressure and said 4high pressure of said source;

3,. Ina transmission, `an input member, an intermediate membergan`output member, a"fr`ont unit providing a plurality of ratios and havingfluid operated means to engage each ratio connecting said input andintermediate members, a rear unit providing a plurality of forwardratios and reverse and having fluid operated meansto engage each ratioconnecting said intermediate and output members, a source of tiuid underpressure including a fron-t unit supply line and a rearunit supply line,selector valve means to selectively connect said front unit supply line-to one of said iluid operated means of said front unit `and said rearunit supply line to one of said iluid operated means of said rear unitin various combinations to provide a plurality of drive ratios for saidtransmissionassembly, valve means responsive to the iiow of uid throughsaid rear unit supply line to cut olf the flow of iluid `through saidfront unit supply line, torque sensing means connected to said inputmember to provide a signal pressure proportional to the torque beingtransmitted by said input member, torque limiting valve means responsiveto said torque signal pressure to limit the pressure supplied to saidfront unit supply line to limit the pressure to said front unit fluid`operated means to limit the torque transmitted by the transmission,means controlled by said selector valve connected to said torquelimiting valve means to control the pressure supplied to said front unitsupply line to vary lthe pressure to said Huid operating means :tocontrol the torque transmitted of iluid under pressurelincluding a`front unit supply line and a rear unitsupply line, selector valvemeansto selectively connect said frontunit supply line to one of said fluidoperated means of said -frontunit and said rear unit supply line to oneof said fluid loperated means of said rear unit in various combinations`to provide a plurality `of drive ratiosfor said transmissionassembly,valve means responsive to the flow of fluid` through said rear -unitsupply' line to cut off the flow of iiuid `through said front unitsupplyline, torque sensing means connected to said input lmember, tof` providea signal pressure proportional to the torque beingtransmitted -by saidinput'member, and torque limiting valve means responsive to said torquesignal pressure to limit the pressure supplied to said front unitVsupply line to limit thepressure` to said front unit iluidoperatedmeans to limit the torque transmitted by the transmission. f

6.; The invention defined by claim 5 and means controlled by saidselector valve connected to said torque limiting valve means to controlthe pressure supplied to said front, unit supply line to vary thepressure to said fluid operating means to lcontrol the torquetransmitted in each ratio bysaidyfront unit to said intermediate shaftto the same torque value. 4

7. The .invention deiined by claim ,5` and means to regulate thepressure of said source at times at a low value and at times at a highvalue in accordance with the operation of the transmission, and saidvalve means being responsive to the same proportion of flow when saidflow of fluid through said rear unit supply line is at said highpressure and said low pressure.

8. In a transmission, an input member, an output member, a lirst unitproviding a plurality of ratios :and having iluid operated means toengage each ratio, a second unit providing a plunality of forward ratiosand having fluid operated means to engage each ratio, said first `andsecond units being connected in series between said input and outputmembers, a source of fluid under pressure including Ymeansnomallypermitting flow through the other of said .supply lines vand responsiveto the flow of uid through oneV of said supply lines to both the onelandthe another fluid operatedvmeans supplied by said one of said'supplylines to cut off theilow of fluid throughsaid other of 'saidlsupplylines.. i,

.9. 'Ihefinvention defined inl claim 8 and said control l Vvalvemeans,disconnecting said source from said other i supply line -`to disengage afluid operated means immediately on 'the initiation of .flow in said onesupply line and connecting saidv sourcerto said other supply line toreengage saidlast mentioned fluid operated vmeans when termined value..y Y Y 10. The invention defined in claim 8 said source having -said tiowin vsaid one supply line is reduced to a predepressure regulatingmeansproviding at times a low pressure level and at timesa high pressurelevel in accordance with predetermined conditions of transmissionoperation, and said control valve means 4disconnecting said source fromsaid other supply line to disengage a fluid operated means immediatelyon the initiation of flow in said one supply line and connecting saidsource to said other supply line to reengage saidlast mentioned fluidoperated means Y Ywhen said flow in said one supply line is reduced to aI predetermined value providing .an engaging pressure havingthe sameproportion to the pressure of said source Yat said high and low pressurelevels. l

11. In `a ytransmission assembly, a multiratio transmissiondrive-tnainhaving aplurality of groups of fluid actuated'ratioV friction engagingdevicesand each of said` i Ygroups having a plurality ofsaid devices,-arranged so that in each drive trainV ratio a ,set ofv at least two ofsaid Y ratio engaging devices, including one in each group, is.engagedto provide each dnive train ratio, a source of uid underpressure, means Vto control `the pressure of the:

vv'fluid from said Ysource to provide a low and la' high iiuid n Y la'.

drive train ratio and to permit engagement-When flow ceases.

13. In a transmission; gear train means including firstY gear meanshaving a plurality of first fluid operated friction engaging meansselectively operative for selectively Y establishing each of a pluralityof first gear means ratio drives, and second gear means connected inseries with saidfirst gear means and having a plurality of secondV fluidoperated `friction engaging means selectively operative for selectivelyestablishing each of V a plurality of second gear means ratio drives;said gear train means beingOperableon the engagement of a selected oneof` said ratiodrives in each of said iirstiand second gear means toprovide afpluralityof gear trainrratios; a source of fluid pressure,valve means to control the supplyof fluid from said source ltoengage aset of saidriluidfactuated ratio .engaging devices, oneV Vin each group,to provide each drive train ratio, Vcontrol. means effective during theengagernent of one of Said ratio' engaging devices in one l group-gtoinsure disengagement of another `of saidv ratio engaging devices in,another groupgoperative in each drive Vratio,lsaid controllmeans beingeffective when saidl one ratio engaging. device is A'engaged to engagesaid'other ratio :engaging device, and means tomodify the action of saidcontrol means to effectv disengagement land engagementof said otherlratio engaging'device when the engaging pressure at-saidone ratioengaging device has' 1 ,the same proportion to said lorvv` pressurel andsaid high pressure'of said source. i

`under pressure; 'shift control meansr operative in each of a pluralityof shift control positions to connect said source to selected pairs ofsaid fluid operated friction engagingv means, each pair including one ofsaid first iiuid operated friction engaging means and one of said secondfluid operated lfriction engaging means yand providing a gear trainratio, and means responsive to a shift change caused by movement of saidshift control means from one posi- Vtion to another position disengagingone of said second fluid operated Vfriction engaging means and engaging1another of said second `fluid operated friction engagingV meansoperative for insuring disengagement of all of Asaid first fluidoperated frictionengaging means until after said anotherof said seconduid operated Vfriction engaging means is engaged Without loadand thenpermitting engagement of the selected one of said operated frictionengaging means under load.V 14. in ya transmission; gear trainmeansincluding first Y gear means having a plurality of first fluidoperated friction engaging means selcetively operative for selectivel'j.establishing each of a plurality' of first gear means ratio drives, andsecond gear means connected in series with said first' gear means andhaving la plurality of second j fluid operated friction engaging meansselectively operavtive for selectively establishing-each offa pluralityof second gear means ratio drives; ksaid gear train means being operableon the engagement of a selected oneof Vsaid ratiodrives in each of saidfirst and second gear means to provide a plurality of gear tnainratiosga source of fluid under pressure; shift controll meansperative ineach of a plurality vof shift Acontrol positions to first con-l nectsaid source to` aselected one of saidjsecond uid j l Voperatedfirictionengaging means for no loadeng'agement and thereafterl to 'connect saidsourcesupply to a selected one of said first fluid operated friction forengagement under load. 15min a transmission; gear train means Lincludingfirst engaging means gearV means having arplurality of first iluidoperated `fricl2. In -a transmission' assembly, a-multiratiotransmis- 'lsion drive train having ya pluralityfofgroups of fluid actuated ratiofriction engaging devices V'vvith, each, group having a plunality of`said -devices each Voperative onV the 4supply vof flu-id'to engage adrive and arranged so that in each ratio a set of said ratio engagingdevices including one in eachV group, is Vengaged to provide each drivetrain ratio, a source of fluid -under pressure, valve means connectingsaid source selectively to sets of said ratio engaging devices tocontrol thesupply of fluid from said source to engage a set of saidfluid actuated ratio engaging devices to provide each drive train ratio,control means responsive tothe flow of fluid from said source to one ofeach set of ratio engaging devices engaged to provide a drive trainratio to insure disengagement of another of said set of ratio engagingdevices engaged to provide a tion engaging means Vselectively operativefor selectively establishing each of a plurality of first gear meansratio drives, and secondV gear means connected in series with said firstgear means' and having a plurality of second il-uid operated frictionengaging means selectively operative for selectively establishing eachof a plurality of second. gear means ratio drives; said gear train meansVbeing Voperable on the engagement of selected groups Veach including aselected one of said ratio drives in each 0f said first and second gearmeans to provide a plurality of gear train ratios; a source of fluidunder pressure; torque measuring means connected to said gear train forproviding a signal varying with thetorque transmitted by saidV geartrain means; first regulator valve means controlled by said signalproviding a rst pressure varying with said torque transmitted by saidgear train means; second regulator valve means providing a secondpressure; shift control means operative in each of a plurality of shiftcontrol positions to first connectV said second regulator valve means tosupply said second pressure to a selected one of said second fiiuidoperated friction engaging means for no load engagement and thereafterto connect said first regulator valve means to supply said firstpressure to a serst fluid Y lected one of said first fluid operatedfriction engaging means for engagement under load; said lfirst fluidoperated friction engaging means being operated by said first pressureto transmit only a limited torque value; and said second fluid operatedfriction engaging means being operated by said second pressure totransmit torque substantially in excess of said limited torque value,

16. In a transmission; gear train means including first gear meanshaving a plurality of first fluid operated friction engaging meansselectively operative for selectively establishing each of a pluralityof first gear means ratio drives, and second gear means connected inseries with said irst gear means and having a plurality of second iluidoperated friction engaging means selectively operative for selectivelyestablishing each of a plurality of second gear means ratio dnives; saidgear train means being operable on the engagement of selected groupseach including a selected one of said ratio drives in each of said firstand second gear means to provide a plurality of gear train ratios; asource of fluid under pressure; torque measuring means connected to saidgear train for providing a signal varying with the torque transmitted bysaid gear train means; first regulator valve means controlled by saidsignal providing a first pressure varying with said torque transmittedby said gear train means; second regulator valve means providing asecond pressure; shift control means operative in each of a plurality ofshift control positions to connect said first regulator valve means tosupply said first pressure to any selected one of said first fluidopenated friction engaging means and to connect said second regualtorvalve means to supply said second pressure to any selected one of saidsecond fluid operated friction engaging means; each of said first fluidoperated friction engaging means being operated by said first pressureto transmit only a limited torque value; and each of said second fluidoperated friction engaging means being operated by said second pressureto transmit torque substantially in excess of said limited torque value.

17.V -In a transmission; gear train means including first gear meanshaving a plurality of -first fluid operated friction engaging meansselectively operative for selectively establishing each of a pluralityof first gear means ratio drives, and second gear means connected inseries with said first gear means and having a plurality of second fluidoperated friction engaging means selectively operative for selectivelyestablishing each of a plunality of second gear means ratio drives; saidgear train means being operable on the engagement of a selected one ofsaid ratio drives in each of said first and second gear means to prolvide la plurality of gear train ratios; a source of fluid un derpressure; shift control means operative in each of a plurality of shiftcontrol positions to connect said source to selected pairs of said fluidoperated friction engaging means, each pair including one of said firstfluid operated friction engaging means and one tof said second fluidoperated friction engaging means for providing a plurality of gear trainratios; torque means connected to said gear means providing a signalvarying with the torque transmitted; and mean connected to said torquemeans opera- 14 tive to control the pressure of the lfluid delivered tothe selected one of said first lluid operated friction means inaccordance with the torque transmitted by said gear means for limitingthe torque transmitted by said gear means to the same value in each gearnatio.

18. In a transmission; gear means having gearing controllable to providea plurality of ratios and a plurality of fluid operated frictionengaging means selectively operative for controlling said gearing toselectively establishing each of a plurality of ratio drives; a sourceof fluid under pressure; shift control means operative in each of aplurality lof shift control positions to selectively connect said sourceto said fluid operated friction engaging means for selectively providingeach of a plurality of gear train ratios; torque means connected to saidgear means providing a signal varying with the torque transmitted; andpressure control means connected to said torque means operative tocontrol the pressure of the fluid delivered to the selected one of saidfluid operated friction means in accordance Iwith the torque transmittedby said gear means to control the engaging force of said Ifluid operatedfriction engaging means to transmit the same torque in the ratio drivesof said gear means.

19. The invention defined in claim 18 and said pressure control meanscontrolling said pressure in response to said torque means and inaccordance with the ratio selected to change the pressure in each gearratio to change the engaging force of the fluid operated frictionengaging means to transmit the same torque in each ratio drive.

20. The invention defined in claim 18 and said pressure control meansreducing said engaging force on a reductionof the torque transmittedduring a change of said ratio drives.

References Cited in the file of this patent UNITED STATES PATENTS1,386,925 Constantinesco Aug. 9, 1921 2,054,377 'Hiavill et al Sept. l5,1936 2,062,523 Miller et al. Dec. 1, 1936 2,454,565 Peterson Nov. 23,1948 2,641,144 Schneider lune 9, 1953 2,642,971 Hagenbook June 23, 19532,646,150 Hobbs July 21, 1953 2,679,170 Prittie May 25, 1954 2,701,974Miller IFeb. 15, 1955 2,715,834 `Chamberlin Aug. 23, 1955 2,724,266Baker et al. Nov. 22, 1955 2,738,689 Dodge Mar. 20, 1956 2,787,920 BlahaApr. 9, 1957 2,794,350 Hart June 4, 1957 2,862,397 Saives Dec. 2, 19582,923,175 Perkins Feb. 2, 1960 2,926,543 Holdeman et al. Mar. 1, 19602,932,988 Flynn et al Apr. 19, 1960 2,978,928 Tuck et al. Apr. 11, 1961FOREIGN PATENTS France I-une 30, 1954 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3, 101 ,O12 August 20, 1963 HowardW. Chrstenson et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 3, line 72, for "of" first occurrence, read or column 5, line 12,for "valve element 173" read valve element 174 column 8, line L12, for'"line 109" read line 198 line 57, for "48" read 38 line 65, for "or"read of Signed and sealed this 14th day of April 1964.

(SEAL) Au t: ERSEST w, SWIDER EDWARD J. BRENNER Attesting OfficerCommissioner of Patents

1. IN A TRANSMISSION ASSEMBLY, A FIRST GEAR UNIT PROVIDING A PLURALITYOF RATIO DRIVES, A SECOND GEAR UNIT PROVIDING A PLURALITY OF RATIODRIVES, CONNECTED IN SERIES WITH SAID FIRST UNIT, CONTROL MEANS TOSELECTIVELY ENGAGE A RATIO DRIVE IN SAID FIRST UNIT AND A RATIO DRIVE INSAID SECOND UNIT TO PROVIDE A PLURALITY OF COMBINATION RATIO DRIVESNORMALLY TRANSMITTING THE FULL POWER APPLIED TO SAID FIRST UNIT, MEANSRESPONSIVE TO A PREDETERMINED VALUE OF TORQUE BEING TRANSMITTED BY SAIDUNITS OPERATIVELY CONNECTED TO SAID CONTROL MEANS TO PARTIALLY DISENGAGETHE DRIVE RATIO ENGAGED IN SAID FIRST UNIT TO CONTINUE TO TRANSMITTORQUE AND TO LIMIT THE TORQUE TRANSMITTED TO A PREDETERMINED MAXIMUMSAFE VALUE TO PREVENT DAMAGE TO THE TRANSMISSION ASSEMBLY.
 2. IN ATRANSMISSION ASSEMBLY, MULTIRATIO TRANSMISSION DRIVE TRAIN MEANS HAVINGMULTIRATIO GEARING AND A PLURALITY OF GROUPS OF FLUID ACTUATED RATIOFRICTION ENGAGING DEVICES EACH HAVING A PLURALITY OF SAID DEVICESOPERATIVE FOR PROVIDING EACH OF A PLURALITY OF DRIVE TRAIN RATIOS ON THEENGAGEMENT OF AT LEAST TWO OF SAID RATIO ENGAGING DEVICES ONE IN EACHGROUP, A SOURCE OF FLUID UNDER PRESSURE, MEANS TO CONTROL THE PRESSUREOF THE FLUID FROM SAID SOURCE TO PROVIDE A LOW AND A HIGH FLUIDPRESSURE, VALVE MEANS TO CONTROL THE SUPPLY OF FLUID FROM SAID SOURCE INEACH RATIO POSITION TO ENGAGE TWO OF SAID FLUID ACTUATED RATIO ENGAGINGDEVICES TO PROVIDE EACH DRIVE RATIO, CONTROL MEANS EFFECTIVE ONLY DURINGTHE ENGAGING MOVEMENT OF ONE OF SAID RATIO ENGAGING DEVICES TO INSUREDISENGAGEMENT OF ANOTHER OF SAID RATIO ENGAGING DEVICES OPERATIVE INEACH DRIVE TRAIN RATIO, SAID CONTROL MEANS BEING EFFECTIVE WHEN SAID ONERATIO ENGAGING DEVICE IS ENGAGED TO ENGAGE SAID OTHER RATIO ENGAGINGDEVICE, AND MEANS TO MODIFY THE ACTION OF SAID CONTROL MEANS TO EFFECTDISENGAGEMENT AND ENGAGEMENT OF SAID OTHER RATIO ENGAGING DEVICE WHENTHE ENGAGING PRESSURE AT SAID ONE RATIO ENGAGING DEVICE IS CHANGEDBETWEEN SAID LOW PRESSURE AND SAID HIGH PRESSURE OF SAID SOURCE.